Duplexer tube status indicator



June 9', 1959 J. L. MoELwAlN nuPLExE; TUBE STATUS INDICATOR Filed sept. 17, 1956 INVENToR .JAY L. Mc ELwAm HIS AGENT.

June 9, 1959 J. L. McELwAlN DUPLEXER TUBE sTATus INDICATOR 2 Sheets-Sheet 2 Filed Sept. 17, 1956 l bi xxxxx xx llllllllllllllllllllllllllll l. l taxa INVENTORZ JAY L. MC ELWAIN,

HIS AGENT United States Patent O DUPLEXER TUBE STATUS INDICATOR Jay L. McElwain, Syracuse, N. assignor to General Electric Company, a corporation of New York Application September 17, 1956, Serial No. 610,272 4 Claims. (Cl. S33-97) This invention relates generally vto the transmission and reception of electromagnetic waves and more particularly to a method and means for providing a continuous indication of the operating status of high-powered duplexers of the polarization twist variety. Reference can be made to Patent 2,735,092 issued to B. P. Brown, Ir. on February 14, 1956, for a detailed description of the manner in which a polarization twist duplexer functions to switch electromagnetic waves between various load circuits.

Polarization twist duplexers depend on the characteristics of individual duplexer tubes for proper operation. Heretofore no method has been available to operating personnel to warn when an individual tube has reached a point in its useful life to where its contribution to overall duplexing performance is negligible or even detrimental. The polarization twist duplexer depends for proper operation on each duplexer tube carrying its share of the load. Failure of one tube therefore results in excessive loading of the remaining good tubes, thereby causing them to fail prematurely. Generally, the failure of a single tube will not produce duplexer breakdown or arcing since duplexers are not normally operated at maximum allowable power. Consequently, by the time the arcing condition manifests itself, not one, but several tubes are defective. Duplexer arcing causes a high standing wave ratio condition to exist in the wave guide, causing danger of damage to the wave source and other associated equipment.

It is therefore an object of the present invention to provide an improved indication of polarization twist duplexer operation.

It is a further object of this invention to provide a continuous indication of individual duplexer tube operation.

It is a further object of this invention to provide advance warning of possible breakdown of particular duplexer tubes.

It is ya further object of this invention to provide an improved arrangement for detecting and replacing defective duplexer tubes.

It is a further object of this invention to provide an improved signal processing arrangement.

For additional objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawings and also to the appended claims in which the features of the invention believed to be novel are particularly pointed out. In the drawing, Fig. 1 is a cutaway view in perspective of a transmit receive switch and waveguide assembly embodying the invention; Figs. 2a and 2b are views of a duplexer tube status indicator; and Fig. 3 is a View of a further embodiment of a duplexer tube status indicator.

Referring to Fig. 1 there is shown a polarization twist duplexing arrangement comprising a circular waveguide 1 which is designed to support the TEUL mode of wave propagation at the normal frequency of operation. A duplexing arrangement such as this is useful to transmit l 2,890,426 Patented June 9, 1959 ponents of the electric field lie in a plane transverse to' the direction of propagation. Furthermore, in a waveguide of circular cross section, the TEu mode has only one axial plane along which the normal component o f the electric vector vanishes, and only one coaxial cylinder along which the tangential component of electric vector vanishes viz., the waveguideboundary itself. For further explanation of this type of waveguide propagation and other types mentioned herein, reference may be made to the previously mentioned patent to B. P. Brown.

Intersecting waveguide 1 is the rectangular waveguide 2 mounted with its longitudinal axis perpendicular to the longitudinal axis of the circular waveguide. Waveguide 2 is oriented with its major transverse axis parallel t0 and its minor transverse axis perpendicular to the longitudinal axis of the circular waveguide 1. The rectangular waveguide is designed'to support only the TEM mode of propagation at the normal frequency of operation.

In the circular waveguide 1 there are inserted a plurality of cylindrical tubes 3. These tubes each have an active length of ionizable medium extending along the diameter of the circular waveguide and `out a short distance into the capped portion 4 which will be described shortly. It should be noted that the succeeding tubes 3 are spaced along the length of the circular waveguide 1 with their longitudinal axes perpendicular to the axis of the guide and the tubes are progressively rotated through substantially equal angular intervals from a vertical plane at the wave entrance side of waveguide 1 t0 a horizontal plane at the wave exit side of waveguide 1. Each tube is sealed and contains an ionizable gas.

When a wave of horizontally polarized electromag-v tion as shown in Fig. 1. For further details of the operation of the tubes and their effect in rotating the electric field polarization, reference may be made to the laforementioned patent issued to B. P. Brown and to.l application 197,027 of .Tabus Barker led November 22,

1950, and assigned to the same assignee.

As previously mentioned, unless tubes are physically*l broken, they decay ygradually from proper to improper operation. The duplexer depends for proper operation on each tube carrying its share of the load. In general, each tube will decay at a different rate. A tube, as it decays, performs a smaller and smaller percentage of the total polarization twist and thus transfers a larger and larger percentage of the load to the succeeding tubes.

This represents excess loading on otherwise good tubfes and causes premature failure. In order to provide advance warning of a possible breakdown or failure, and to present a continuous indication of the condition of each tube, individual indicators 4 are provided. These indicators receive a portion of each tube 3 extending.'

through the wall of the waveguide 1. The indicators operate on the principle that good tubes, when in the presence of high power R-F energy, have relatively high electromagnetic radiation near their ends while defective f tubes have no end radiation or at best very little.

Referring to Fig. 2a there is shown one embodiment of a dupleXer tube status indicator. The duplexer tube status indicator comprises a comicctor plug 5 having its plug-in end threaded at 6 to mate with the threaded portions of the waveguide rib 7. A duplexer tube 3 protrudes into the hollow portion of rib 7 and is seated with in the threaded rib portion by means of a metal mesh gasket 8 which is compressed into supporting operation with the duplexer tube by operation of the threaded gland nut 9. As previously mentioned, upon ionization of the ionizable medium, which may be argon gas shown as 1Q contained within the walls of duplexer tube 3, the end portion of the duplexer tube protruding outside the main Wall of Iwaveguide 1 radiates radio frequency energy in the principal coaxial TEM mode. The electric field is mostly normal to the tube 3. It is this component which couples through the guide and into the coaxial line formed by the ionized duplexer tube 3 and the inside surface of plug S. However, the parallel component of E, which is actually shown, is required to start and maintain the ionization in the tube during the time of the radio frequency pulse propagating down the main guide 1. The connector plug 5 constitutes in effect a coaxial line with an inner conductor 11 which is spaced from the protruding tip of the duplexer tube 3 in a manner to provide suitable capacitive coupling between the ionized gas column and the inner conductor 11. The connector 12 comprises a standard BNC female connector 5 which mates with the BNC male connector portion 12. A portion of 12 is knurled to provide rapid attach-detach operation of the male and female connector portions. The socket portion of 12 comprises a bayonet type connection for receiving a neon glow tube 13 such as the common NE-Sl type. A cap 14 is provided for insertion over the neon glow tube 13. This cap has a plurality of openings 15 whereby the operation of the neon glow tube may be checked. Thus in operation, upon ionization of the ionizable medium 1t) contained in the duplexer tube 3, an effective coaxial coupling is provided between the gas column and the neon glow tube 13. Depending upon the status of the duplexer tube 3, the neon glow tube will glow to indicate the corresponding condition of the duplexer tube. Upon aging of the duplexer tube 3 the neon glow tube 13 `will glow dimly or not at all since a reduced amount of radio frequency energy is made available in the end portion of the duplexer tube. A simple study of Fig. 2 reveals that the attach-detach features and the use of threaded connector portions permit ready replacement of the neon glow tube 13 and the duplexer tubes 3.

Referring to Fig. 3 there is disclosed a further embodiment of a dupleXer tube status indicator. Plug portion 16 comprises a threaded end portion which mates with the threaded end portion of the waveguide rib 7. An opening 17 is provided in the waveguide portion for admitting a portion of the dupleXer tube 3. Gland nut 9 cooperates with the threaded portion of the waveguide ribbing to compress the metal mesh gasket or washer 8 into supporting position with respect to the end of the duplexer tube. Metallic spring fingers contained on the centering cap 18 physically contact the wall portion of the duplexer tube 3 protruding outside the waveguide 1 and provide conductive contact with the inner conductor of the bayonet type socket contained within the plug 16. The spring fingers and cap 18 are separated from the inner wall of the plug 16 by means of the insulating bushing 20. A neon glow tube 13 is received by the bayonet socket portion of the plug 16. Thus upon ionization of the ionizable medium 10 contained in the end portion of the duplexer tube 3, electromagnetic waves from within waveguide 1 are capacitively coupled from the gas column to the spring fingers 18. The plug 16 operates in effect as a coaxial line arrangement between the dupleXer tube 3 and the neon glow tube 13. The neon glow tube glows to a degree dependent upon the operating condition of the duplexer tube. A transparent or translucent plastic cap 21 is provided for covering the neon glow tube. This cap is threaded to mate with the corresponding threads on the plug 16 and thereby permit ready removal of the neon glow tube. A knitted or woven mesh cap 22 made of, for example, Monel metal is provided over the neon glow tube. This metal mesh cap contacts the walls of the plug and serves as a shield to prevent radio frequency energy from being radiated outside the duplexer tube status indicator.

Thus it is seen that applicants invention provides a novel, convenient and useful indicator for describing the status of a duplexer tube. The specific mechanical configuration of the indicator furthermore permits ready replacement of the individual indicator components and of the dupleXer tube itself. Also by referring to Fig. 4, there is shown a modification of the invention which readily permits actual measurements to be made of individual duplexer tube operation. Meter 23 can be readily coupled through a suitable detector 25 such as a theimistor or bolorneter by means of cable and plug assembly 24 to the connector 5 to obtain power or wave signal measurements.

While a specific embodiment has been shown and described, it will, of course, be understood that various modifications may be made without departing from the invention. The appended claims are therefore intended to cover any such modifications within the true spirit and scope of the invention.

What I claim and desire to secure by Letters Patent of the United States is:

l. In combination, a waveguide for propagating electromagnetic waves therethrough, a duplexer tube mounted within said waveguide for controlling the propagated elecn tromagnetic waves and responsive only to waves propagated within said `waveguide having an intensity above a predetermined level, a portion of said duplexer tube extending outside said waveguide, a glow tube responsive to the electromagnetic waves radiated by said portion of said duplexer tube for indicating the operating condition of said duplexer tube, and a coaxial transmission line dimensioned to couple the energy of said electromagnetic waves radiated from said portion to said glow tube, whereby said glow tube is caused to indicate the operating condition of said dupleXer tube.

2. An arrangement for indicating the condition of a duplexer tube mounted within a waveguide and operative to control electromagnetic waves propagated through the waveguide comprising, a gaseous glow device and a coaxial transmission line forcoupling a portion of the energy of said waves to said glow device, said duplexer tube being dimensioned to have its ionizable medium operate in part as the inner conductor of said transmission line for coaxially coupling said energy a part of the way to said glow device and in part as a radiating element for radiating said coaxially coupled energy a further part of the way to said glow device, said glow device being arranged to respond to electromagnetic waves radiated by said medium for providing an indication of the operating condition of said duplexer tube.

3. An arrangement for indicating the operating condition of a dupleXer tube mounted within a waveguide and operative to change the wave propagation characteri'stics of such waveguide wherein the duplexer tube cornprises an elongated vessel containing an ionizable medium and said medium being responsive only to waves propagated in said guide having an intensity above a predetermined level for becoming ionized sufiiciently to change said waveguide propagation characteristics comprising an indicator circuit, a coaxial transmission line comprising an inner and outer conductor coupled to said waveguide for coupling out a portion of the energy of said waves propagated in said waveguide, a portion of said medium forming said inner conductor, said portion of medium constituting the end of said inner conductor most remote from its coupling to said waveguide and being dimensioned to radiate said coaxial line coupled energy, and said indicator circuit responsive to said radiated energy.

4. In combination, a waveguide for propagating electromagnetic waves, a duplexer tube device containing an ionizable medium passing across said waveguide and extending outside said waveguide, said ionizable medium normally non-ionized and responsive to propagated waves having an intensity above a predetermined level for becoming ionized sufliciently to alter the transmission characteristics of said waveguide, means for coupling outside said waveguide a relatively small portion of the energy of said waves propagated within said waveguide com prising said portion of said ionizable medium extending outside said waveguide, said portion of medium adapted References Cited in the le of this patent FOREIGN PATENTS Great Britain Jan. 26, 1955 OTHER REFERENCES Lets Use Neon Bulbs, Q.S.T. Amateur Radio, pages 22-25, July 1953, vol. 37, No. 7. (Copy in Div. 51.) 

